Halogen Bonding‐Enabled Stabilization of Copper(I) Cluster Scintillators in Aqueous Environments

Abstract Scintillators are essential in applications, such as homeland security, nuclear physics, and geological exploration. However, conventional scintillators often suffer from degradation under polar chemical conditions, resulting in scintillation quenching and structural decomposition. Here, a molecular engineering strategy is demonstrated to enhance scintillator stability and performance through halogen‐bonded lattice reconstruction. The synthesis of a copper cluster scintillator, (X‐MBA)4Cu4I4 (X: Br or Cl, MBA: S‐methylbenzylamine) is reported, where halogen bonding improves lattice symmetry and rigidity, effectively suppressing electron‐phonon coupling and defect trapping. The halogenated copper clusters exhibit a photoluminescence quantum yield of ≈90%, a 13‐fold increase in light yield, and an X‐ray detection limit of 28.8 nGyair s−1, outperforming halogen‐free counterparts. These scintillators maintain their structural integrity and performance even after prolonged exposure to polar chemical solvents. The combination of molecular design and structural robustness enables high‐resolution X‐ray imaging (22 lp mm−1) across various chemical environments, paving the way for high‐performance scintillators with exceptional durability and efficiency.